Ion implantation is a commonly used process in the manufacture of semiconductors and also in other technologies. For example, surface hardening of tools may be accomplished using ion implant techniques. The principle interest and application of this invention, though not the exclusive ones, are in the manufacture of semiconductors.
Ion implantation equipment is described in many texts and in the literature generally, see, for example, U.S. Pat. Nos. 2,750,541, 2,787,564, and 2,842,466, as well as ENCYCLOPEDIA OF SEMICONDUCTOR TECHNOLOGY, John Wiley & Sons (1984), pp. 397 et seq., Kirk Othmer ENCYCLOPEDIA OF CHEMICAL TECHNOLOGY, article on "Ion Implantation", John Wiley & Sons, and the treatise ION IMPLANTATION, J. K. Hirvonen, ed., Academic Press (1980). Descriptions of such apparatus and uses therefor are found in many other patents, see, for example, U.S. Pat. Nos. 3,457,632, 3,445,926, 3,434,894 and 3,390,019.
Ion implantation technology involves the ionization of an atom of the material to be implanted, accelerating the ion toward the target, a chip or slice of silicon in the present instance, which is to become a semiconductor device or which is a semiconductor device the properties of which are to be modified. The ion beam is focussed to impact a desired area or pattern on the target. The entire operation is carried out in a high vacuum and requires ultra-high purity ion source reagents.
Ion implant equipment is very expensive and is economically used only when operated during a relatively high production rate and with minimum down time. Down time results each time a new ion source must be loaded because of the necessity to restore the vacuum in the system and produce a controlled beam of ions. Thus, it is of the greatest importance that the introduction of a new ion source material be accomplished quickly with minimum interruption of production.
Extremely dangerous reagents such as arsine and phosphine, and other very toxic and sometimes explosive reagents, have been used as ion source materials. These materials are suitable for use in a technical sense but present serious safety risks and the need for extreme safety precautions.
Solid ion source materials, such as various salts of phosphorus, arsenic, boron, etc., are greatly preferred for safety reasons, but solid semiconductor dopants have presented serious technical and operating problems and are not entirely satisfactory. Extended down time problems, poor product quality, etc. have resulted from the difficulty of introducing such source materials into the ion implant equipment.
The present invention offers a simplified method of handling ion source materials and for introducing the same into ion implant equipment which is safe and which minimizes down time and loss of production.